Electrical control system



Jan. 2, 1945. KLEMPERER 2,366,197

ELECTRICAL CONTROL SYSTEM Filed April 22, 1942 2 Sheets-Sheet l l l lgll Y 5%; a 77 -67 +,v W' T\T 6 9 66 m 68 i74- 7s- 76 L. 72 55 a0 46 57 64M 49 \JO 5 3 \NVENTOR.

HANS KLEMPERER,

' BY [24m 91 5F 1/ 2 TTY.

Jan. 2, 1945. KLEMPERER 2,366,197

ELECTRICAL CONTROL SYSTEM v Filed April 22, 1942 2 Sheets-Sheet 2|NVENTOR. HANS KLEMPE ER,

ATTY.

Patented Jan. 2, 1945 ELECTRICAL CONTROL SYSTEM Hans Klemperer, Belmont,Mass., assignor to Raythcon Manufacturing Company, Newton, Mass., acorporation of Delaware Application April 22, 1942, Serial No. 440,019

6 Claims.

This invention relates to electrical systems of type which are adaptedto supply intermittent pulses of current by the successive discharge ofone or more condensers. More particularly, this invention refers tocondenser welding systems.

In certain condenser Welding systems it is de-- sirable that the pulsesof welding energy follow each other as rapidly as possible. However,there are limitations as to the speed with which successive weldingpulses may be made due to the necessity of preventing overlapping ofpulses, and to the further necessity of allowing a sufficient intervalto permit the electrical energy storage means, such as for example,condensers, to store an adequate amount of electrical energy beforedischarging the energy therefrom. It has been customary heretofore afterthe condenser has been discharged into the load to allow a given amountof time to elapse before the condenser is again discharged. In order toinsure against overlapping of impulses and in order to allow thecondenser to be fully charged, said time intervals have been madecomparatively long. In allowing a sufiicient margin of safety so thatthese conditions may be met, these intervals have been made so long thatthe speed of operation of such systems has been reduced. It is an objectof this invention to provide a system which may be operated at themaximum possible speed, the condenser being discharged immediately uponthe decay of a previously supplied pulse and upon the charging of thecondenser to a predetermined level.

Another object of the present invention'is the provision of means forpreventing the discharge of a condenser in such a system until saidcondenser has been fully charged.

Other and further objects of this system will become apparent, and theforegoing objects will be best understood, from the followingdescription of exemplification thereof reference being had to thedrawings in which Fig. 1 is a schematic diagram of a seam welding systemembodying my invention; and

Fig. 2 is a schematic diagram of another seam welding systemrepresenting a modified embodiment of my invention.

In Fig. 1, Welding current is to be supplied to a pair of rotatablewelding electrodes or wheels l adapted to roll on the work 2 which is tobe Welded. The current is to be supplied to the electrodes in successivepulses of welding current so as to perform successive weldingoperations. Each welding operation welds a spot on the work 2, thesespots preferably overlapping so as to form a continuous seam welding.The electrodes l are connected to the secondary 3 of a weldingtransformer 4. This welding transformer is provided with a core member 5made of magnetic material. The welding transformer 4 is also providedwith a tapped primary winding 6 adapted to be energized by the dischargefrom a relatively large condenser l. Condenser I is adapted to becharged from any suitable source of direct current such as a directcurrent generator, battery, rectifier or the like. For this purpose, thecondenser may have its positive side connected to a terminal 9 and itsnegative side connected to a terminal 8, terminals 9 and 8 being adaptedto be connected to the positive and negative sides, respectively, of asuitable source of direct current.

Condenser l is designed to be discharged alternately and in oppositevectorial directions through the halves of the primary 6 of the weldingtransformer 4. For this purpose the positive side of condenser 1 isconnected directly to the tap H! of the primary winding 6. The negativeside of condenser 1 is connected to opposite ends of the primary winding6 by separate controlled ignition discharge tubes ll and 12. These tubesare preferably of the pool cathode type and are each provided withanigniter for initiating a cathode spot on the pool in order to cause saidtubes to conduct current. This igniter may be of the electrostatic typeconsisting of a conductor separated and insulated from the cathode by athin glass layer. Tubes I l and are provided with cathodes I3 and M,respectively, said cathodes being connected to the negative side ofcondenser l. Anode I5 of tube II is connected to end l6 of the primarywinding 6 while anode ll of tube I2 is connected to end l8 of primarywinding 6. Igniting impulses are supplied to the igniter ll) of tube IIfrom the secondary 20 of the igniting transformer 2i. Similarly, igniter22 is supplied with igniting impulses by being connected to thesecondary 23 of an igniting transformer 24. Igniting transformers 2| and24 are provided with primar windings 25 and 26, respectively.

Igniting impulses are supplied to the primaries 25 and 26 by condensers21 and 28, respectively.

Condensers 21 and 28 may be charged from any suitable source of directcurrent, such as for example, a battery 29 which has its negative enddirectly connected to the negative sides of condensers 21 and 28. Thepositive side of said battery may be connected to said condensersthrough a manually-operable switch 30 in series withboth said condensersand separate resistances 3| and 32 in series with condensers 21 and 28,respectively. Resistances 3| and 32 limit the current supplied to saidcondenser and control the char ing rate.

In supplying igniting impulses to the primary 25, condenser 21 has itspositive side directly connected to one end of said primary, thenegative side of said condenser being connected to the connecting arm 33of a ratchet relay 34, said arm 33 being adapted to make contact witheither of two contacts 35 or 36 in said relay. Contact 35 is connectedto the other end of the primary winding 25. Similarly, condenser 28 hasits positive side directly connected to one end of primary winding 26and its negative side connected to arm 33. Contact 36 is in turnconnected to the other end of primary winding 25. It will be seenthatwhen arm 33 makes contact with contact 35 condenser 21 will bedischarged through primary winding whereas if arm 33 makes contact withcontact 36, condenser 28 will be discharged through primary winding 26.Thus, as arm 33 connects with contact or 36, it supplies ignitingimpulses to tubes H or l2, respectively.

The movement of arm 33 between contacts 35 and 36 is determined in therelay herein described by current supplied to the coil 39 of said relayand associated mechanism. The relay 34 is of the type in which themovement of arm 33 from contact to contact is produced by succeedingpulses of current supplied to the coil 39 thereof, each pulse of currentmoving the arm away from one contact and to the other, the next pulse ofcurrent moving the arm from said other contact back to the firstcontact, etc. Thus, by supplying a succession of pulses of current tocoil 39 arm 33 alternately makes contact with contacts 35 and 36 andthereby alternately discharges condensers 21 and 28 to thereby ignitetubes H and I2 alternately, thus discharging condenser T alternately andin opposite vectorial directions through the halves of primary winding6.

Pulses of current for actuating relay 34 may be supplied to the coil 39of said relay from any suitable source, such as for example a condenser49. Condenser 40 may be charged by said battery 29 in series with acurrent limiting resistance 38. Condensers 40 has its positive sidedirectly connected to one end of coil 39 by a gaseous rectifying tube4|, said gaseous rectifying tube being controlled to control thedischarge of condenser 40 through the coil 39 of relay 34. Tube 4| hasits anode 42 connected to one end of the coil 39 and its cathode 43,which may be of the permanentl energized type, such as a filamentarycathode, connected to the negative side of condenser 40. Tube 4| ispreferably provided with two control grids 44 and 45.

It will be seen that whenever tube 4| conducts, ratchet relay 34 will beoperated and will cause either tube H or tube |2 to fire to therebproduce a pulse of welding current through the primary 6 of the weldingtransformer 4. As stated hereinbefore, it is an object of this inventionto produce succeeding welding pulses as rapidly as possible. Thus, tube4| is designed to conduct and to cause arm 33 of ratchet relay 34 tomove from contact to contact as soon as any previously supplied pulse ofcurrent in the primary winding 6 has completely decayed, and thecondenser "I has been fully charged. Therefore, means are provided inthis system for preventing conduction of tube 4| when any pulse ofcurrent is passing through primary winding 6 and when condenser is notfully charged.

For preventing conduction of tube 4| when any pulse of current ispassing through primary winding 6, I preferer to utilize means, such asthose described in my copending application, Serial No. 435,979, filedMarch 24, 1942 for Electrical control system. Such means are preferablyresponsive to the flow of current in the primar winding 6 of the weldingtransformer 4 and are adapted to derive a potential therefrom to producea negative bias on grid 44 of tube 4|. Tube 4| is so designed that theapplication of a suitable negative bias to either grid 44 thereof or togrid 45 will prevent said tube from conducting. In order to derive apotential from the pulse of current supplied to primary winding 6. Iprefer to provide a circuit including an impedance arranged in shuntacross each half of the primary winding, the potential drop producedacross said impedance providing the cutoff bias for grid 44 of tube 4|.For this purpose, I prefer to utilize a constant voltage device such asa glow discharge device 46. One side of the glow discharge device 46 isconnected directly to tap ID of primary winding 6. The other end 41 ofsaid glow discharge device 46 is connected in series with a currentlimiting resistance 48 and a rectifying tube 49 to end H; of primarywinding 6. The rectifying tube 49 may be a gaseous tube having a cathodeof the permanently energized type. The cathode 50 of tube 49 isconnected to end N5 of primary winding 6, and the anode 5| of said tubeis connected to resistance 48. Similarly, the glow discharge tube 46 isconnected across the left side of primary winding 6 by connecting side41 thereof through a resistance 52 and a rectifying tube 53 to end l8 ofprimary winding 6. Tube 53 may be similar to tube 49 and may be providedwith a permanentl energized cathode 54 which is connected to end l8, andwith an anode 55 connected to resistance 52. Side-41 of glow dischargetube 46 is connected to the grid 44 of tube 4|. Since the cathode 43 oftube 4| is connected to the center tap ID of primary winding 6, it willbe seen that when a difference of potential is produced across said glowdischarge tube 46, this potential will be impressed between grid 44 andcathode 43.

The drop in potential across glow discharge tube 46 is produced whenevercurrent flows through either half of the primary winding 6 as will beapparent from the following. If, for example, tube fires, condenser 1will discharge into the right side of primary winding 6. A potentialdrop will be produced across said primary winding upon the firing oftube II with end l6 of said winding being negative relative to centertap ID. The potential across the right side of primary winding 6 will beimpressed across the shunt circuit arranged thereacross comprising tube49, resistance 48 and glow discharge tube 46. Since this potential willbe in the correct vectorial direction with negative potential on thecathode of tube 49 and positive potential on the anode thereof, tube 49and glow discharge tube 46 will both fire. A voltage drop will beproduced across the glow discharge tube 46 with side 41 thereof beingnegative relative to the potential on the center tap ID. This voltagedrop will be impressed on tube 4| between its grid 44 and its cathode 43and will thereby prevent said tube from conducting. Similarly, when tubeI2 is fired and a pulse of current flows through the 2,366,197 left sideof primar winding 6, the shunt circuit consisting of rectifying tube 53,resistance 52 and glow discharge tube 46 will conduct current andthereby produce a drop in potential across the glow discharge tube 46which drop of po tential is impressed between grid 44 and cathode 43 andserves to prevent tube 4| from conducting.

Because of the inductance associated with the Welding load, thedischarge of condenser I through either half of the primary winding 6tends to be oscillatory and the potential across both halves of saidwinding tends to reverse as the condenser I discharges therethrough. Inorder to make each welding current impulse substantially unidirectionalwith exponential decay, a pair of controlled ignition discharge tubes 56and 51, preferably of the same type as tubes II and I2, is provided.Tubes 56 and 51 have their cathodes 58 and 59, respectively, connectedtogether and to tap II] on the primary winding 6. Anode 60 of tube 56 isconnected to end I6 of the primary winding 6, while anode 6| of tube isconnected to end l8 of the primary winding. Tubes 56 and 51 are providedwith igniters 62 and 63, respectively, preferably of the type heretoforedescribed in connection with tubes H and i2. These igniters are suppliedwith igniting impulses from the secondary windings 64 and 65 of ignitingtransformers 66 and 61, respectively. Primaries 68 and 69 of ignitingtransformers 66 and 61 are adapted to have igniting impulses suppliedthereto. For this purpose one end of each of said primaries areconnected together and to top In of the primary winding 6 of the welding4 transformer. The other end of primary winding 68 is connected to a tap10 on a resistance 1|. One end of resistance TI is connected to tap H)of the primary winding 6, the other end of said resistance beingconnected to the cathode 12 of a rectifying tube 13 having its anode I4connected to end l6 of the primary winding 6. Tube 13 may be a gasfilled rectifying tube having a permanently energized cathode. Similarlythe other end of the primary 69 of igniting transformer 61 is connectedto a tap 15 on a resistance 16, one end of resistance 16 being connectedto the tap ill of primary winding 6 while the other end of resistance I6is connected to the cathode 11 of a rect fying tube 18 which has itsanode 19 connected to end l8 of the primary winding 6. Rectifying tube18 is preferably of the gaseous type provided with a permanentlyenergized cathode. When the potential across either side of said primarywinding 6 reverses, the gaseous rectifying tube 13 or 18 associated withsaid side will conduct current and a voltage drop will be produced inthe resistance 1| or T6 in series with said tube to thereby supply anigniting impulse to the igniting transformer 66 or 61. These ignitingimpulses will cause either tube 56 or tube 51 to fire thereby providingfor the exponential unidirectional decay of current through theassociated half of the primary winding 6.

It will be seen that, when the potential in either half of the primarywinding is reversing and the potential across said winding is zero,neither tube 49 nor tube 53 will be conducting and no potential dropwill be produced across glow discharge tube 46 for maintaining a cut-offbias on tube 4|. In order to maintain this cut-off bias during theextremely short interval in which both tube 49 and tube 53 are notconducting, I prefer to provide a condenser 80 across said glowdischarge tube 46, said condenser being charged during the time currentis flowing through the glow discharge tube 48, said condensermaintaining a cut-off bias when current is no longer flowingtherethrough. A resistance 8| is provided across condenser 80 todischarge said condenser so that the condenser maintains the cut-offbias on tube 4| for only a short time during the reversal of potentialacross either of the halves of the primary winding 6.

From the foregoing description it will be seen that when tube II isignited and condenser 1 discharges through the right side of primarywinding 6, tube 49 conducts and a voltage drop is impressed upon tube 4|and prevents operation thereof. The potential in the right side ofprimary winding 6 declines to zero and tube 49 as well as glow dischargetube 46 ceases to conduct. The cut-off bias will be maintained on tube4| by condenser 80 until the potential across the right side of primarywinding 6 reverses. When this potential across the right side of primarywinding 6 reverses a potential will be induced in the left side ofprimary 6 in a vectorial direction which will cause tube 53 to conductand tube 46 will also then conduct, a constant voltage drop beingproduced across glow discharge tube 46 which will be impressed upon tube4| and prevent conduction in said tube. A similar operation occurs whentube I2 is ignited with tube 53 first conducting, and after thepotential across the left side of primary winding 6 has reversed, tube49 then conducting. From the foregoing it will be seen that whenever apulse of current is flowing through either half of the primary winding 6of the welding transformer 4, a cut-off bias will be applied to tube 4|to thereby prevent said tube from conducting and operating ratchet relay34. I have hereinabove described how tube 4|, which upon conductionoperates the ratchet relay 34 to fire either tube II or I2, is preventedfrom conducting whenever a pulse of current is how ing in the primary 6.In accordance with my invention tube 4| is also prevented fromconducting until condenser I is charged to a predetermined level.Charging of the condenser to a predetermined level before dischargethereof is essential in many condenser systems, particularly incondenser welding systems where discharge of the condenser before'it isfully charged will produce non-uniform and inadequate welds. It istherefore essential in such systems that the condenser be fully chargedbefore being discharged. In the systems illustrated in the drawings.this is accomplished by preventing tube 4| from conducting and therebydischarging condenser until condenser I has been charged to apredetermined level.

To prevent tube 4| from firing. I prefer to apply a cut-off biaspotential to the first grid 45 of tube 4| as long as condenser 7 isunde'rcharged. To control the application of thi cut-off bias, I preferto provide a tube 82 which is preferably of the vacuum type having apermanently energized cathode 83 and a control grid 84. Tube 82 has itsanode 85 connected through a suitable tapped resistance 86 to thepositive side of battery 29. The cathode 83 of tube 82 is connected tothe negative side of battery 29 and to the positive side of condenser 1through a source of reference potential, the reference potential beingderived from a source of direct current such as a battery 81 having theresistance 88 of the potentiometer 89 connected thereacross, thepositive side of said battery being directly connected to the negativeside of battery 29 and the positive side of condenser 1. The arm 90 ofpotentiometer 89 is connected to the cathode 83. Grid 84 is connected tothe arm 9| of the potentiometer 92 having its resistance 93 connectedacross condenser I. Tap 94 of resistance 86 is connected in series witha suitable grid-resistor to the grid 45 of tube 4|. This circuit, whichis adapted to prevent conduction in tube 4| when condenser I isundercharged, operates in the following manner. It will be seen thatbattery 81 applied a positive bias to the grid 45 which is in serieswith the bias supplied to the charge on condenser I and is vectoriallyopposite thereto. When condenser 'I i undercharged the constants of thecircuits are such, (and these may be adjusted by varying potentiometers89 and 92), that positive potential is applied to the grid 84, thispotential being sufficient to cause tube 82 to conduct. When tube 82conducts a voltage drop is produced acrOSs resistance 96, this voltagedrop being in a direction to produce negative cut-off bias on tube 4| tothereby prevent said tube from conducting. As condenser I is charged,the potential derived from said condenser through potentiometer 92increases until it exceeds the potential derived from battery 81 andthereby applies a negative bias to grid 84 of tube 82. When condenser Iis fully charged this negative bias is of a sufiicient magnitude to cutoff conduction in said tube. Grid 45 of tube 4| thereupon becomespositive and tube 4| will conduct, providing grid 44 is also positive,this last depending upon whether any pulse of current is still alive inthe primary winding 6 of the welding transformer 4.

From the foregoing description it will be seen that I have invented acondenser discharge system which is adapted to operate at a hi h rate ofspeed, limited solely by time required to charge the condenser of suchsystems and the time required for pulses of energy, delivered by saidcondenser, to decay. In the system described in connection with Fig. 1,I have described tub 4| as controlling the operation of a ratchet relayand thereby controlling the ignition of the ignition discharge tubes.However, instead of a ratchet relay other firing controls may beemployed. In Fig. 2 a novel means for firing the ignition dischargetubes is illustrated.

Referring now to Fig. 2, the same numerals used in Fig. l have beenapplied to elements thereof which are the same as, and which function ina manner similar to, like-numbered parts in Fig. 1. In Fig. 2 the pulsesof current derived from tube 4| are applied to the primary 95 of atransformer 96 instead of to the coil 39 of ratchet relay 34 asdescribed in Fig. 1. The pulses appearing in the secondary 9'! of thetransformer 96 are used to alternately initiate conduction in a pair ofgaseous rectifying tubes 98 and 99. For this purpose one end of thesecondary 97 is connected separately in serie with resistances I00 andIIII to the grids I02 and I03 of tubes 98 and 99. respectively. Theother end of said secondary 91 is connected to the cathodes I04 and I05of tubes 98 and 99, respectively. Cathodes I04 and I05 may be uf thepermanently energized type. In order to hold off conduction in tubes 98and 99 until pulses are applied to said tubes from the secondary 91, asuitable source of direct current I06, such as for example a battery,may be used to apply a negative bias to the grids of tubes 98 and 99.The battery I06 has the positive side thereof connected to the cathodesof said tubes and the negative side thereof connected in series with aresistance I01 to a point intermediate resistances I00 and IN andthrough said last-mentioned resistances to the grids I02 and I03,respectively.

Upon the firing of either tube 98 or tube 99 an igniting impulse isadapted to be delivered to the primary 25 and 26 of ig itingtransformers 2| or 24, respectively. To provide anode potential for saidtubes a source of direct current I06, such as for example a battery, maybe employed. The battery I08 has its negative side connected to thecathodes I04 and I 05. The positive side of battery I 08 is connected toone end of each of the primaries 25 and 26 of the igniting transformers2| and 24, respectively, the other ends of said primariesbeing connectedto the anodes I09 and H0, respectively. It will be seen that when eithertube 98 or tube 99 conducts, the igniting transformer having its primaryin series with said tube will receive an igniting impulse.

In the system illustrated in Fig. 1, each time tube 4| conducts, a pulseof energy is supplied to one of the igniting transformers, these pulsesof energy being impressed alternately on the primaries 25 and 26. InFig. 2, in.order to alternately supply igniting transformers 2| and 24with igniting impulses, tubes 98 and 99 are adapted to conductalternately. To cause said bes to conduct alternately, I prefer toarrange a pair of condensers III and H2 in the following manner.Condenser III is connected to anode I09 of tube 98 and to grid I03 oftube 99. Similarly, condenser I I2 is connected to anode III) of tube 99and to grid I02 of tube 98. A relatively large condenser H3 in serieswith a choke coil H4 is connected between anode I09 and anode ||0. Arectifier H5 i connected across primary 25 of igniting transformer 2|and a similar rectifier H6 is connected across primary Winding 26 ofigniting transformer 24.

Whenthe firing arrangement is assembled, condensers H2 and H3 arecharged by battery I08, the sides of said condensers connected to thegrids being negative. While battery I06 tends to charge said condensersin an opposite vectorial direction, said battery is much smaller thanI08 and therefore a substantial charge in the direction first indicatedwill be produced by battery I08.

Thereafter, when tube 4| conducts and a pulse of current is therebyproduced in the secondary 9'! of transformer 96, this pulse of currentapplies a positive voltage to the grids I02 and I03 of tubes 98 and 99,respectively. Due to the in herent unbalance of such systems either tube98 or tube 99 will begin conducting first. Assuming tube 98 begins toconduct first, the positive side of condenser III will be connectedthrough tube 98 to the cathode I05 of tube 99 and thus a potential willbe impressed be tween the grid I03 and cathode I05 of tube 99. thepotential on the grid being negative. Tube 99 is thereby prevented fromconducting. The conduction of tube 98 will produce a firing impulse inthe primary 25 of igniting transformer 2|. Condenser |I3 will also becharged when tube 98 is conducting, the charging current derived frombattery I08 flowing from the positive side thereof through the primary26 of igniting transformer 24, through choke coil IN to condenser ||3,and thence from the other side of condenser II3 through tube 98 to thenegative side of the battery I09. The value of choke coil H4 is such asto prevent a peaked pulse of current which might cause ignition of tubeI2 from appearing in the primary 26 of igniting transformer 24.Condenser II 3 will be charged so that the side thereof towards anodeI09 will be negative. Since condenser III is comparatively small it willdischarge in a comparatively short time, but the value of condenser IIIwhich is selected is of such value that such condenser is not dischargedbefore the pulse produced in the secondary 9I oi. transformer 96 hassubsided. When the next pulse is produced in the secondary 91, tube 99will fire. The firing of tube 99 will produce an igniting impulse in theprimary 26 of igniting transformer 24 and at the same time will applythe charge of condenser II3 between the anode I09 and the cathode I04 oftube 98 and tube 98 will go out. 98 stops conducting the flux in thecore of transformer 2| will collapse and the current produced therebywill flow through rectifier I I5 which has a comparatively lowresistance. Thus the flux will collapse without producing a substantialvoltage in the secondary of .the transformer 2i. When tube 98 goes outcondenser III again becomes charged while condenser I I2 is dischargedthrough tube 99. As tube 99 conducts, con-- denser I I3 is charged bybattery I08 through primary 25 and through tube 99, the side ofcondenser II3 towards anode IIO of tube 99 becoming negative. When thenext pulse of current flows in secondary 91 of transformer 96, tube 98will fire and the charge on condenser II3 will be thereby impressed ontube 99 between its anode IIZ and its cathode I05. Thereupon tube 99will go out.

From the foregoing it will be seen that each succeeding pulse in thesecondary 91 of transformer 96 alternately fires tubes 98 and 99,thereby alternately providing igniting impulses to the primaries 25 and26 of igniting transformers 2| and 24. The firing system hereinbeforedescribed is capable of extremely high speed operation.

While I have described the details of two embodiments of my invention itwill be apparent that numerous changes might be made without departingfrom the teachings thereof. For example, I have shown a system fordischarging one condenser into a welding load. It will be apparent thatinstead of a welding load the condenser may be adapted to discharge intoany trolling the flow of current through a pair of circuits, a source ofelectrical energy impulses, said source including a control tube havinga plurality of control electrodes adapted to control the flow of currenttherethrough in response to a plurality of operating conditions of saidcontrolled circuits, a pair of electrical space discharge tubes eachhaving a cathode, an anode, and a grid, means for coupling each of saidcathodes to one terminal of said source, means for coupling each of saidgrids to the opposite terminal of said source, a condenser, meansconnecting one pole of said condenser to one of said anodes, meansconnecting the opposite pole of said condenser to the other of saidanodes, a pail-of loads each connected in series with one of said tubes,and separate means coupling the anode of each tube to the grid of theother tube.

2. In an electrical control system for controlling the flow of currentthrough a pair of cir- When tube V cults, a source of electrical energyimpulses, said source including a control tube having a plurality ofcontrol electrodes adapted to control the flow of current therethroughin response to a plurality of operating conditions of said controlledcircuits, a pair of electrical space discharge tubes each having acathode, an anode, and a grid, means for coupling each of said cathodesto one terminal of said source, means for coupling each of said grids tothe opposite terminal of said source, a condenser, means connecting onepole of said condenser to one of said anodes, means connecting theopposite pole of said condenser to the other of said anodes, a pair ofloads each connected in series with one of said tubes, and separatemeans coupling the anode of each tube to the grid of the other tube,each ofsaid coupling means including a condenser.

3. In an electrical control system a pair of space discharge tubes eachhaving a cathode, an anode, and a grid, a source of potential having ahigh voltage terminal connected to each of said anodes and a low voltageterminal connected to each of said cathodes, a pair of loads each inseries between one of said tubes and said source of potential, a sourceof energy impulses having one terminal connected to each of saidcathodes and an opposite terminal connected to each of said grids, acondenser having one pole connected to one of said anodes and theopposite pole connected to the other of said anodes, a pair ofcross-connections each connecting the anode of one of said tubes to thegrid of the other of said tubes and a condenser in each of saidcross-connections.

4. In an electrical control system a pair of loads, a source of current,a circuit for supplying electrical energy impulses from said sourcealternately to each of said loads, a pair of electrical space dischargetubes in said circuit, each associated with one of said loads andadapted upon conduction thereof to connect its corre-- sponding load tosaid source, each of said tubes having an anode, a cathode, and controlmeans for controlling conduction thereof, means for producingintermittent electrical energy impulses independently of the conductionof said tubes, said last named means being connected to both of saidcontrol means to supply energy impulses simultaneously to said controlmeans, anda condenser adapted to be charged in opposite vectorialdirections by the conduction of said tubes, the conduction of either ofsaid tubes impressing the charge of said condenser on the anode andcathode of the other tube in a direction to stop conduction of saidother tube, and upon further conduction charging said condenser in theopposite vectorial direction.

5. In an electrical system for firing controlled ignition dischargetubes, a pair of igniting transformers, a source of current, a circuitfor supplying electrical energy impulses from said source alternately toeach of said igniting transformers, a pair of electrical space dischargetubes in said circuit, each in series with one of said ignitingtransformers and adapted upon conduction thereof to connect itscorresponding igniting transformers to said source, each of said tubeshaving an anode, a cathode, and control means for controlling conductionthereof, means for producing intermittent electrical energy impulsesindependently of the conduction of said tubes, said last named meansbeing connected to both of said control means to supply energy impulsessimultaneously to said control means, and a condenser adapted to becharged in opposite vectorial directions by the conduction of saidtubes, the conduction of either of said tubes impressing the charge ofsaid condenser on the anode and cathode of the other tube in adirectionto stop conduction of said other tube, and upon further conductioncharging said condenser in the opposite vectorial direction.

6. In an electrical control system a pair of 10 loads, a source ofcurrent, a circuit for supplying electrical energy impulses from saidsource alternately to each of said loads, a pair of electrical spacedischarge tubes in said circuit, each

